This invention relates in general to capillary electrophoretic systems and in particular to an improved capillary zone electrophoretic system for detection of substances.
Capillary zone electrophoresis (CZE) in small capillaries has proven useful as an efficient method for the separation of solutes. An electric field is applied between the two ends of a capillary tube into which an electrolyte containing the solutes is introduced. The electric field causes the electrolyte to flow through the tube. Some solutes will have higher electrokinetic mobilities than other solutes so that the sample components are resolved into zones in the capillary tube during the flow of the electrolytes through the capillary.
CZE is advantageous since it requires only very small sample volumes such as the contents of a cell or cellular subcompartments. For these and other reasons, CZE has shown great promise as a separation and detection technique.
One of the major challenges in CZE is to improve selectivity and sensitivity of detection. To improve selectivity of detection, it is desirable to employ detectors which respond only to certain sample components but not to others; this permits detection of the origin of certain sample components despite chemical changes and the presence of other components and substances. Since the amounts of materials used in CZE are so minute, detectors used must have high sensitivity. One way to increase detection selectivity and detection sensitivity is to use radio-labels. In "Presentations on High Performance Electrophoresis at the 1988 Pittsburgh Conference", LC.GC, Vol. 6, No. 6, pp. 484-491 at 488, a radioactive detection technique designed for capillary electrophoresis is described for detecting pharmaceuticals labelled by a radio-label containing technetium, a gamma emitter with a six hour half life. A capillary tube containing the radio-labelled pharmaceutical is passed through a hole drilled in a scintillation crystal. The latter emits light when gamma rays strike it. By passing the sample through a capillary tube enclosed by a scintillation crystal, activation of the scintillation crystal by radiation is permitted from all sides of the capillary. This technique was presented in the 1988 Pittsburg conference by Altria, Simpson, Bharij and Theobald.
The above-described method is not entirely satisfactory. It is therefore desirable to provide an improved electrophoretic system employing radioactive detection.
In conventional capillary zone electrophoresis, the time period during which a detector can be used for detecting a substance is constrained by the speed of movement of the sample zone through the capillary. Consequently, the detection of minute quantities of substances may be difficult. It is therefore desirable to provide an improved capillary zone electrophoretic system in which such difficulty is alleviated.